1921 UNDELIVERED REGISTERED MAIL USA TO LONDON. Envelope sent registered mail Cambridge.Mass. USA to London with US 2c and 10c cancelled CAMB/MASS oval hand stamps, on reverse ms "Not Known". Boxed "Undelivered for reason stated/To be returned to sender at the address shown..." and on reverse fine strike of the scarce REGISTERED/RETD LTR SECTION oval date stamp 4 OCT 21. Fine usage. (Ref 98901).
